Medical nebulizer

ABSTRACT

A medical nebulizer has a reservoir for medical liquid, a capillary nozzle having a proximal end for receiving liquid from the reservoir and a distal end connectable to an inspiration gas flow path to deliver liquid droplets into an inspiration gas flow, a pump for supplying liquid from the reservoir through the capillary nozzle, and a regulator for regulating the delivery of the liquid to a predetermined amount. The pump supplies the liquid in a continuous flow throughout the delivery of the predetermined amount and a stimulator, such as a piezoelectric vibrator, is provided for vibrating the distal end of the nozzle to stimulate droplet formation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a medical nebulizer and in particularto a medical nebulizer for providing a nebulized physiologically activeliquid into an inspiration gas flow of a mechanical breathing aid.

2. Description of the Prior Art

Medical nebulizers are often used to deliver a metered dose of aphysiologically active liquid into an inspiration gas stream forinhalation by a recipient. They generally operate to generate liquiddroplets which form an aerosol with the inspiration gas. In othercircumstances medical nebulizers may be used to inject water dropletsinto an inspiration gas stream to provide gas with a suitable moisturecontent to a recipient, this is particularly useful where theinspiration gas stream is provided by a mechanical breathing aid such asa respirator, ventilator or anaesthetic delivery system.

The term “medical liquid” as used herein means any liquid, regardless ofwhether it is physiologically active, which is to be supplied to theairways of a recipient.

A known medical nebulizer is described in PCT Application WO 95/01137and is a hand held device which operates to eject droplets of a medicalliquid into a passing air stream (inspiration gas stream) which isgenerated by a recipient's inhalation through a mouthpiece. This knowndevice has a reservoir for the medical liquid which is connected to acapillary nozzle via a pump which operates directly on liquid within thecapillary to eject liquid droplets through the nozzle and into aninspiration gas flow conduit. The pump is a bubble jet or piezoelectricpump, both of which are pulsed to eject a droplet through the nozzlewith each pulse. A control unit is also provided to regulate the dosebased on the number of pulses provided to the liquid by the pump, forexample by regulating the time that a drive signal of known frequency isapplied to the piezoelectric element of the pump.

A problem with this device is that the dosage is dependent on the pulsefrequency. This limits the device to the delivery of relatively smalldoses unless a number of nozzle and pump arrangements are employed. Thiswould increase the overall size of the device. Moreover when thepiezoelectric pump is used the supply of a pulse to the piezoelectriccrystal can stimulate the crystal to produce a pulse train of typically5 to 6 pulses and lead to an inaccurate dose being provided.Furthermore, the pump is necessarily relatively small as it must actonly on liquid within the capillary. The pumping power of such a pumptends to be limited so that at small capillary bore sizes flowresistance can become a problem, limiting the minimum droplet size totypically, microliters.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a medical nebulizerwhich overcomes the pumping problems associated with the above-describedknown device.

The above object is achieved in accordance with the principles of thepresent invention in a medical nebulizer having a reservoir containing amedical liquid and a capillary nozzle having a first end communicatingwith the reservoir for receiving the medical liquid therefrom, and asecond end connectable to an inspiration gas flow path in communicationwith a patient. A pump supplies the medical liquid from the reservoirthrough the capillary nozzle in a continuous flow, and a regulatorregulates the delivery of the liquid to the nozzle so as to supply apredetermined amount of the medical liquid thereto. A stimulator ismechanically connected to the second end of the capillary nozzle and isoperated to vibrate the second end of the capillary nozzle to stimulatedroplet formation, so that droplets of the medical liquid are suppliedinto the inspiration gas flow.

By arranging for the pump to supply a continuous stream of liquid to benebulized with the aid of a stimulator for vibrating the nozzle ametered dose of medical liquid can be provided in droplet form withoutthe need to monitor the number of droplets.

Moreover, by using a pump which does not act directly on liquid withinthe capillary a more powerful and less expensive pump, for example asyringe pump, may be used. This enables the capillary bore size to bereduced over known nebulizer and picoliter sized droplets may besupplied. The finer droplet formation allows a more homogeneous vapor tobe formed in the inspiration gas stream and a more efficient uptake ofthe medical agent by the patient.

The reservoir and the nozzle may be releasably couplable. In this waythe reservoir may be readily disposed of, replaced or removed forsterilizing as necessary. This also provides an administrative benefitin that an estimate of the amount delivered can be readily obtained froma count of the used reservoir cartridges, enabling for example, stocksto be timely replenished. The pump may be operated continuously andsuitable valving provided, such as micro-valves which have particularlywell defined cut on and off characteristics, to limit the supply ofliquid in order to deliver the predetermined dose from the nebulizer. Inthis manner inaccuracies in the delivered dose due to the start up andshut down characteristics of the pump can be alleviated.

In order to co-ordinate the delivery of the liquid dose with aninspiration of a recipient, which may be either before, during or afteran inspiration, a flow meter can be provided in the flow path of theinspiration gas and adapted to control the delivery dependent on asensed gas flow.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a ventilator apparatus having anebulizer according to the present example.

FIG. 2 is a schematic illustration of a nebulizer according to thepresent invention usable in the ventilator arrangement of FIG. 1.

FIG. 3 is a schematic illustration of a handheld nebulizer according tothe present invention.

FIG. 4 is a schematic illustration of a further embodiment of thenebulizer according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 a ventilator apparatus is generally shown in which electroniccontrol signal flow paths are shown by the arrows connecting elements ofthe apparatus. A conventional ventilator 1 is shown having a number(here two) of input gas lines 2,3 for different gasses and an evacuationgas line 4. Patient breathing conduits 5,6 are provided for transportingbreathing gas between the ventilator 1 and lungs 7 of a patient via aY-piece 8 and endotracheal tube 9. The common branch of the Y-piece 8 isconnected to the tube 9 and the separate branches are connected torespective conduits 5,6 in order to provide a flow path 5,8,9 forbreathing gas from the ventilator 1 to the patient (inspiration gasflow) which is separate from a flow path 9,8,6 for breathing gas fromthe patient to the ventilator 1 (expiration gas flow). One-way valves10,11 are placed in associated conduits 5,6 in order to ensure thecorrect direction of travel of breathing gas. A flow meter 12 is placedin the inspiration flow path 5,8,9, for example downstream of theone-way valve 10 in the inspiration gas flow direction.

A nebulizer 13 according to the present invention is also provided forsupplying water vapor to the inspiration gas flowing to the patientslungs 7 through a capillary nozzle 14 connected to the flow path 5,8,9.The nozzle 14 is disposed to provide the liquid preferably as close tothe patient as possible and typically at the Y-piece 8.

A moisture meter 15 is also provided to monitor the moisture content ofthe inspiration gas after passing the nozzle 14 and to provide anindication of the measured moisture content to a control/dispenser unit16 of the nebulizer 13 where it is used to control the dosage incombination with gas flow information from the flow meter 12.

The operation of the nebulizer 13 will be further explained withreference also to FIG. 2. The nebulizer 13 shown in FIG. 2 includes thecontrol/dispenser unit 16 and a nozzle unit 17 which are in fluidcommunication by means of a conduit 18 which, at one end, is releasablyconnected to the proximal end of the capillary nozzle 14. Thisreleasable connection may be made using any conventional fluid tightconnecting means and is here a press fit connection through an O-ringseal 19. The nozzle unit 17 is also releasably connected to the Y-piece8 of the ventilator apparatus of FIG. 1, again using a push fit O-ringseal 20. It will be apparent to those skilled in the art that with thisarrangement various parts of the nebulizer 13 may be convenientlyreplaced or removed for cleaning.

The opposite end of the conduit 18 is connected to a syringe pump 21 viaa controllable on/off valve 22 which are within the control/dispenserunit 16. Also within this unit 16 is disposed a microprocessor basedcontrol unit 23, an oscillator driver unit 24 and a pump power supply25.

The pump power supply 25 is adapted to continuously pressurize liquidwithin the syringe reservoir 26 of the syringe pump 21 during theoperation of the nebulizer 13 with the dosage being controlled via theon/off valve 22 and the control unit 23.

The oscillator driver unit 24 is also adapted to continuously supply ahigh frequency (typically in the region of 1 MHZ) drive signal to apiezoelectric oscillator 27 which is disposed within the nozzle unit 17to vibrate the distal end of the capillary nozzle 14 to stimulatedroplet formation in a manner similar to that well known in the art ofink-jet printing. The oscillator unit 24 may be adapted to vary thefrequency of the drive signal in dependence of the liquid used, its flowrate and preferred droplet size in order to enhance the operationalflexibility of the nebulizer 13 (it is well understood that droplet sizedepends on, among other things, the liquid flow rate through the nozzle14, the viscosity of the liquid, and vibrational frequency).

In use, power is provided to the oscillator drive unit 24 and the pumppower supply unit 25 from a mains supply via an on/off switch (notshown) accessible externally of the control/dispenser unit 16 and whichoperate continuously while the nebulizer 13 is switched on. An inputsignal 28 from the moisture meter 15 of FIG. 1, indicative of themoisture content of inspiration gas, and an input signal 29 from theflow meter 12 of FIG. 1, indicative of the presence and magnitude of aninspiration gas flow, are provided to the control unit 23. The dosage ofwater from the reservoir 26 necessary to provide the desired relativehumidity (which may be user variable or a fixed value) of theinspiration gas is then determined within the control unit 23 and asignal 30 is output to operate the valve 22 to achieve the determineddose. In the present case it is assumed that the flow of water from thesyringe pump 21 is predetermined and programmed into the control unit23. A flow meter (not shown) may be included to directly measure theflow of fluid within the conduit 18, the value of which will be usedwithin the control unit 23 in the regulation of the flow through thevalve 22 in order to achieve the determined dose.

In FIG. 3 a nebulizer is shown which is intended for use without amechanical breathing aid. A mouthpiece 31 defines an inspiration gasconduit 32 having an inlet 33 open to the atmosphere and an outlet 34intended for insertion into a patient's mouth. A nozzle section 35 isreleasably screwed into the mouthpiece 31 so that liquid droplets canpass from distal ends of a number of capillary nozzles (here two) 36,37into the inspiration gas conduit 32. A piezoelectric oscillator 39, ismechanically coupled to the nozzles 36,37 to vibrate their distal endsand is provided with an externally accessible electrical contact 40 towhich oscillator drive signals can be applied. It will be appreciatedthat the nebulizer of FIG. 3 may be readily modified to include anoscillator drive unit, with or without a battery power supply, toprovide a more fully portable nebulizer.

Proximal ends of the nozzles 36,37 are connected to a common liquidreservoir 38 in which is contained a physiologically active liquid. Theliquid reservoir 38 is releasably connected to a one-way valve 40, forexample using a press fit or screw thread connection for ease ofreplacement. The valve 40 is arranged to prevent through flow towardsthe gas conduit 32 until pressure from the liquid exceeds a pre-setamount just above atmospheric. This amount is chosen so that liquid fromreservoir 38 cannot flow through the valve 40 under the pressure of itsown weight.

The reservoir 38 has a readily deformable container which is housed in aholder 41 having at least one wall section 42 formed of elasticallydeformable material such that as the section 42 is squeezed thereservoir deforms to expel liquid through the valve 40. A rigid end-cap43 is provided to push fit over the holder 41. This cap 43 providesphysical protection for the elastic wall section 42 against accidentaldeformation and unintended release of liquid from the reservoir 38. Thereservoir 38 may be sized to control the dose provided to the patient sothat a single dose will be delivered when the reservoir 38 is fullysqueezed.

FIG. 4 shows a nebulizer useful, for example, in the treatment of weakor unconscious patients who are breathing without the aid of amechanical breathing aid. A common flow section 44 defines a gas conduit45 having a first aperture 46 open to the atmosphere and a secondaperture 47 intended for gas connection to a patient's mouth via a facemask 48. A nebulizer unit 49 is connected to the gas conduit 45 througha wall of the common flow section 44 so that liquid droplets can passfrom distal ends of a number of capillary nozzles, which may be vibratedseverally or separately using a piezoelectric vibrator within thenebulizer unit 49. The number of nozzles actually used to supply theliquid droplets can be less than the total number of nozzles providedand selected, for example, dependent on a desired rate of supply ofnebulized liquid. Moreover, nozzles having a variety of different sizescan be included to further increase the flexibility in supplycharacteristics of the nebulizer.

A pump unit 50, such as the syringe pump described with respect to FIG.1, is operably connected to the capillary nozzles of the nebulizer unit49 via a valve unit 51 and includes a medical liquid reservoir (notshown) from which liquid is pumped through the nozzles of the unit 49 toform a vapor in gas within the conduit 45. A control unit 52, such as adedicated microprocessor or a suitably programmed personal computer, isalso provided to control the operation of the vibrator within thenebulizer unit 49, the valve unit 51 and the pump unit 50 to supply thefluid in dependence of a signal from a flow sensor 53 within the gasconduit 45 of the common flow section 44 indicating a patient'sinspiration phase. The control unit 52 can be programmed to operate thepump unit 50 to tend to supply a continuous stream of liquid through thenozzle section 49 and to control the valve unit 51 to open and close andprovide a desired amount of medical liquid to the patient.Alternatively, the pump unit 50 can be operated intermittently in orderto provide the desired amount of medical liquid. In both alternativesthis desired amount can be either pre-set in the control unit 52employed as a user input, or the control unit 52 can be provided with auser interface.

Although modifications and changes may be suggested by those skilled inthe art, it is the intention of the inventor to embody within the patentwarranted hereon all changes and modifications as reasonably andproperly come within the scope of his contribution to the art.

I claim as my invention:
 1. A medical nebulizer comprising: a reservoircontaining a medical liquid; an inspiration gas flow path adapted todeliver inspiration gas to a patient; a capillary nozzle having a firstend communicating with said reservoir for receiving said medical liquidtherefrom and an open second end in direct communication with saidinspiration gas flow path; a pump for supplying liquid from saidreservoir through said capillary nozzle in a continuous flow; aregulator for regulating delivery of said medical liquid to said secondend of said nozzle in a predetermined amount; and a stimulator inmechanical connection with said second end of said capillary nozzle forvibrating said second end to convert said continuous flow of medicalliquid into droplets, said droplets being delivered into saidinspiration gas flow directly from said second end of said capillarynozzle.
 2. A medical nebulizer as claimed in claim 1 wherein saidregulator comprises a valve arrangement operable to limit supply of saidmedical liquid through said capillary nozzle to said predeterminedamount.
 3. A medical nebulizer as claimed in claim 1 further comprisinga power supply for said pump, and wherein said regulator regulates saidpower supply to limit the supply of said medical liquid through saidcapillary nozzle to said predetermined amount.
 4. A medical nebulizer asclaimed in claim 1 further comprising a flow meter in said inspirationgas flow path which emits a signal dependent on inspiration flow in saidinspiration gas flow path, and wherein said regulator is supplied withsaid signal from said flow meter and regulates the delivery of saidmedical liquid dependent on said inspiration flow.
 5. A medicalnebulizer as claimed in claim 1 wherein said pump comprises a syringepump.
 6. A medical nebulizer as claimed in claim 5 wherein said syringepump contains said reservoir, and wherein said reservoir contained insaid syringe pump is releasably couplable to said first end of saidcapillary nozzle.
 7. A medical nebulizer as claimed in claim 1 whereinsaid inspiration gas flow path comprises an inspiration gas flow path ofa mechanical breathing assist apparatus.
 8. A medical nebulizer asclaimed in claim 1 wherein said capillary nozzle is a first capillarynozzle, and wherein said medical nebulizer further comprises pluralityof additional capillary nozzles, each having a first end incommunication with said reservoir and a second end in communication withsaid inspiration gas flow, and each having an individual amount of saidmedical liquid delivered therethrough in a continuous flow by said pump,the respective individual amounts collectively comprising saidpredetermined amount, and wherein said stimulator is connected to all ofthe respective second ends of said capillary nozzle for vibrating all ofsaid second ends to produce droplets which are introduced at saidrespective second ends into said inspiration gas flow path.